Out of the pall of night, dead upon the Black Bullet, there suddenly charged a grotesque sky monster—a strange, caterpillar-treaded behemoth which spewed a torrent of lead as it came. What was it? And from where did it come? These questions raced through the Griffon's mind as he leveled his guns upon it. But before he could draw a bead, two great arms reached from the back cockpit, pinned him in a vise-like grip. Barney O'Dare—his own man—had turned against him.

THE Black Bullet streaked across the sky like a two-bladed knife hurled by some unseen giant. It dipped, swerved and turned, wheeling through its nocturnal gyrations under the skilled hand of the Griffon. Below, slashing alternately across the waters of Long Island Sound and the velvet black rollers of the broad Atlantic, the sword-blade shaft of light from the Montauk beacon brought out the indistinct outlines of surface craft below—a Boston steamer, a proud puffing tug, a palatial yacht.

Above it all, the Black Bullet raced against a stop watch on the Griffon's wrist. It answered his every whim, sped through the full catalog of maneuvers demanded by the man in the scarlet mask. In the back seat, proud of his handicraft and his mechanical skill, Barney O'Dare, the Griffon's none-too-silent partner, likewise sat watching the black amphibian go through her paces after a thorough overhaul.

The Griffon turned to smile over his shoulder, then stiffened abruptly.

A grim, winged fortress was charging down on them from above. In the fraction of a second, the Griffon took it in completely, focused his camera-eye on its striking details.

It was a huge mid-wing monoplane powered with four massive engines of the in-line type. These motors were set in beautifully-faired nacelles. At the nose of the long, protruding fuselage was a movable gun turret flaunting a short, snub-nosed weapon that gleamed in the starlight and flare of the exhausts. It was larger in bore than the average machine gun and the Griffon winced at the thought of what might be hurled from that black snout.

Barney was doing nothing but stare. That was not like Barney. Usually he had to be restrained. He just sat hunched, peering out through the closed gun tray of the transparent coupe top.

The Griffon watched the flying fortress wheel, then gasped at its amazing undercarriage. This appeared to be a complete unit in itself. Instead of wheels, it had a complete set of caterpillar tractor treads.

"Whew!" whistled the Griffon. "If she needs something as strong as that, she must be heavy. What the devil sort of a bus is it?"

PUN-N-NG!

A flash of flame stabbed out of the nose of the monster with the strange silver body. A shell hissed past the Black Bullet and the Griffon screamed: "Get that guy in that turret, Barney!"

But Barney was not "buying" any. He simply sat back and stared with an insane glint in his eye at the thunderous bus that was pounding steel at them. He appeared to be strangely fascinated.

The Griffon threw the Black Bullet clear, curled into a climbing turn. Then he reached over, snatched at Barney's shoulder, and shook him. "Wake up, you dumb Mick!" he yelled. "What are you waiting for?"

Satisfied that the O'Dare would finally go into action the Griffon returned to his front-office business and made ready for a general sally on the wide-winged, giant that was now below them.

Again that snorting big gun barked and another screeching shell slammed past and burst in mid-air above them.

BRR-OOOM!

The Griffon flew madly now, hurled the Black Bullet all over the sky, sought an opening to get a punch at the silver-bodied fortress below. Finally he worked the Black Bullet into a position dead behind the tail flippers of the big machine, preparing to give her every thing he had up front.

"Get him on the twist, Barney, after I get through with her," the Griffon bawled over his shoulder.

He nosed down, gave the big Avia all she could take, and pressed every gun trigger in the office.

But before he could really draw a bead, something smothered him from behind. Two great arms were encircling him, constricting his own arms to his sides. The move caused him to draw the stick back and the Black Bullet went up the sky like a released rocket. For several seconds they remained at this angle and finally the Griffon's arms were released.

THE Griffon swore under his breath, turned his enraged attention to getting the Black Bullet back on an even keel. He had to ease her gently to prevent a spin. He had no desire to throw the ship about any too hard, for he did not know how much, if any, damage had been done to his own craft.

Finally he pulled her clear and hammered away to get out of range of the strange ship. He wondered why Barney had done that. He wondered what the Mick had seen to cause him to take such a strange attitude. This was a new one on the Griffon.

By the time he had cleared, the winged fortress was out of sight.

"What the hell?" he started to bawl over his shoulder. "What the deuce made you do that, Barney?"

He got no answer, so he twisted around farther, saw that Barney was still staring out of the side of the cockpit with unseeing eyes. He had not broken out the guns and he had no answer.

"Are you drunk?" the Griffon finally asked.

No answer.

"Oh well, there's no use sitting up here arguing. We'll have it out when we get down."

The Griffon turned the Black Bullet back toward the Long Island shoreline and rammed in the Skoda mufflers which deadened the roar of the big Avia down to a low purr. He throttled back and let her glide gently in.

She dropped on the water a few minutes after Keen had lowered the retractable pontoons and surged up with a minimum of noise to the flat, hard-packed sands in front of a boathouse. Then quietly, with no more noise than would be offered by a luxurious motor car, the Black Bullet, her pontoons tilted now for land movement, rolled past a heavy foliaged grape arbor and up a thicklyturfed lawn.

Barney slipped out, rammed his hand inside the fuselage, and the wings folded back snug against the sides of the fuselage. Then he moved forward, sought a sunken switch box at one end of a great rock-garden and in a few seconds the face of the garden mysteriously split open and folded back, disclosing a cavernous hangar.

The Griffon ran the ship inside and climbed out, prepared to get some explanation of Barney's amazing actions.

But Barney was nowhere to be found. He had disappeared completely!

Kerry Keen drew off his Griffon garments, let out a low whistle. Finally he turned on a light to inspect the damage done to the Black Bullet, and then, satisfied that she had suffered no untoward battering, he snapped the switch off and wandered, pained, puzzled and discouraged, upstairs to his snug den.

THAT was shortly before midnight; but it was well after 8 o'clock before Keen got up from his big desk where he had been working on a paper entitled The Magnus Effect on the Spinning Projectile which he was to read before the coming International Ballistics Commission conference. He had the weird quality of being able to completely throw his mind off past events to concentrate on the work at hand. By the time he was ready for his glass of warm milk, which Barney always had at hand by the time he was ready to slip between the sheets, he had to jostle himself to recall the incident of the flying fortress and the strange disappearance of the Mick.

"That's right," he said.

"Now where the devil did he bust off to?"

He went through the great house, seeking his man, but he was nowhere to be found.

His room had not been entered since he had left it prior to going on the test flight. He was nowhere about in the sunken hangar. He was not in the wine cellar, nor were there any empty O'Doul's Dew bottles around.

Keen frowned, lit a massive, straight-stemmed briar pipe. He sat down again and pondered on the subject, wondered what was behind Barney's mind when he interfered with his diving on the great plane over the Sound.

There seemed to be no answer for it, so Keen sanely went to bed—to sleep on it, as it were.

NEXT morning, there was no cheery breakfast, no warm bath, no laying out of a neatly pressed morning suit. Keen, hair tousled and puffyeyed, wandered about Graylands like a lost dog. He peered into rooms, sought evidence of Barney's return and even looked about for a note. There was nothing. And so, he made himself a light breakfast and continued work on his ballistics paper.

But by noon he could stand it no longer, so he ran out his sport roadster, a new Italian Renghali, and throwing a light top coat into the seat beside him, he started out for New York City. By three o'clock he was sitting in the dingy office of John Scott, Department of Justice agent, in the midtown section of the city.

Drury Lang was there, looking even rattier than ever. Both Scott and Lang were working feverishly over broken sections of metal—something that looked like a battered taxi-meter and some sections of frayed wire.

"Trying to get London?" inquired Keen, with a smirk toward Lang. "Or is this something new in parlor games."

"You can get out of here as quick as you like. We're busy," growled Lang.

"Do anything for you?" inquired Scott a little more sociably, but businesslike nevertheless. "We've got a rather nasty job on our hands."

"But I want every hospital and police station in this section checked," said Keen. "Every one, understand?"

Both Lang and Scott looked up suddenly, Lang dropped the parts of metal he was studying and came over to where Keen was sitting. "What's up?" he said quickly. Lang had never seen Keen like this before.

"He disappeared last night from the house— about 11 o'clock. Just went, and he hasn't turned up yet."

"What was the matter? You bawl him out for something?"

"No, but I was going to. He disappeared before I could get around to it."

"Well, there you are, then," Scott said, throwing out his hands. "He must know the wrath of your tongue, and he was not having any."

"No, that wasn't it. I've bawled him out before, but it never leaves any impression. This time, I'm afraid, it's something serious. I want you to make a thorough search."

"Or what?" growled Lang.

"Or.... or I won't tell the Griffon to do you any more favors," smiled the ballistics expert.

"Bosh! You've never even seen the Griffon," raged Lang. "I have!"

"So I've heard," Keen taunted. "But look here, I do want you to make an attempt to locate Barney. I do miss him you know."

"This ain't no lost and found department," Lang spat again. "Besides, I told you we're busy. Maybe," he added, "you heard about that taxicab business yesterday afternoon.... in 84th Street?"

"No. What taxicab business?"

"That one that blew up, killing the driver and injuring about ten people who were nearby."

"Oh yes, another variation of the Wall Street explosion business wasn't it? I read something about it in the papers."

"This is what did it," said Lang with a proud gesture at the twisted metal on the desk.

"The meter?" asked Keen getting up and showing interes...

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